The invention discloses a method for preparing chromium-containing iron powder by direct reduction of calcium-free chromium slag, which belongs to the technical field of comprehensive utilization of chromium slag. The method comprises the following steps of: firstly, material preparation, wherein the calcium-free chromium slag is mixed with a reducing agent and fluxing agents comprising alumina, and the four-element alkalinity m(MgO+CaO) / m(SiO2+Al2O3) of the mixed material is equal to 0.9 to 1.3; secondly, agglomeration, wherein the mixed material is pressed or pelletized to obtain agglomerates; thirdly, reduction roasting, wherein the agglomerates are roasted in reducing atmosphere at a reduction temperature of 1,250 to 1,350 DEG C for 30 to 240 minutes; fourthly, crushing and fine grinding, wherein the roasted agglomerates are crushed and ground to be fine; and fifthly, magnetic separation, wherein the finely ground powder is subjected to magnetic separation at magnetic induction intensity of 100 to 200 mT, thereby separating the chromium-containing iron powder. According to the method, the calcium-free chromium slag is completely detoxified and fully recycled, the grade sum of calcium and iron in the prepared chromium-containing iron powder is over 80 percent, the chromium recovery rate and the iron recovery rate are respectively over 78 percent, and the method is low in energy consumption and free from secondary pollution.